Weekly Update With Dr. Crystal Hepp: Tracking Coronavirus In Wastewater

May 13, 2020

Scientists at Northern Arizona University’s Pathogen and Microbiome Institute are tracking the coronavirus in an unusual way—by taking samples of sewage. In places where people are infected, the virus ends up in untreated wastewater. The scientists are sampling the virus’ genetic material in the greater Flagstaff area and on the Navajo Nation to see if they can quickly pinpoint spikes in the disease. In KNAU’s weekly update on the science of COVID-19, Melissa Sevigny spoke with infectious disease expert Dr. Crystal Hepp about the research.   

Crystal Hepp
Credit Northern Arizona University


So you’re tracking this virus in wastewater. Tell me how that works exactly.

There’s a lot of human testing going on, especially with the testing blitz that’s going on Arizona, but that sort of testing is probably not going to be sustainable over the long term. What we’re trying to do is add a secondary layer of surveillance. Let’s say there are some communities haven’t had many cases of coronavirus yet… What wastewater surveillance can do when it’s used weekly or even multiple times per week, is if the virus is circulating in asymptomatic individuals, we might be able to pick it up in the wastewater prior to it causing a high number of human cases. That could trigger downward public health intervention strategies, such as maybe increasing social distancing in certain communities.

 I know it might be early days, but what have you discovered so far.

We found that in areas where we thought we would get positives, we were able to detect the virus. In areas where there have been fewer cases we have not detected the virus, as well. So that’s why we’re really trying to work on this viral concentration method, to increase our chances of detecting the virus in these areas where there are fewer cases.

Tell me more about how you hope this information can help public health officials in our area.

We can actually use the assay results to estimate how many people in a community are infected, so it can give us an idea of the magnitude of the outbreak. When we layer on genomic sequencing with that, we can see how many different variations of the virus are present in the community and that also can help us to better understand the magnitude of the outbreak, especially when considering how fluid the public health interventions are right now, with social distancing increasing, decreasing… And then, final, Flagstaff and northern Arizona in general is really a tourism hotspot. We have so many things that people from all around the world love to come see. With that, with the loosening restrictions and people coming here to visit us, we do expect they’ll be introductions from other parts of the world, other parts of the United States, into Flagstaff. Wastewater surveillance will help us see where those introductions are from and how many there have been, and that can also help inform public health strategies, maybe certain parks will need to be closed down for longer because they’re bringing in too many people

I understand you’re also testing water after it’s gone through the treatment process. What have you found there?

Our expectation was that the wastewater treatment process was going to successfully decontaminate the water if any virus was present, and that’s exactly what we found. There are a lot of places in town where reclaimed water is used for watering grass… We don’t think there is a risk for coronavirus being present in that wastewater.

What are the next steps in this research?

We have several different partners in Flagstaff, Munds Park, Kachina Village, and also on the Navajo Nation, we would like to expand our partners a funding allows…. I think that overall wastewater could be a powerful tool for public health surveillance purposes, not just now when we’re in the middle of this great pandemic, but also over time it could be used to trigger to the community’s awareness of norovirus, enteroviruses, a lot of different viruses that are present. We don’t plan on this project being just a one-off because of the coronavirus pandemic, we would like to continue this for the foreseeable future to help Flagstaff, northern Arizona, and other residents of Arizona, be more aware of viruses that could be circulating at any point at time so they can take precautions.

Crystal Hepp, thank you so much for speaking with me today.

Thank you so much, have a good day.